Grinding method and apparatus



Oct. 16, 1951 L, O Q 2,571,324

GRINDING METHOD AND APPARATUS Filed Dec. 26, 1947 A Hubert L. Ymm

INVE TOR.

ATTORNEY Patented Oct. 16, 1951 GRINDING METHOD AND APPARATUS Robert L. Young, Indianapolis, Ind., assignor, by mesne assignments, to The Marquette Metal Products Company, Cleveland, Ohio, a corporation of Ohio Application December 26, 1947, Serial No. 793,971

3 Claims.

This invention relates to internal centerless grinding and more particularly to a method and means for gripping and holding a cylindrical or tubular shaped article while its inner diameter or bore is being precision ground, with especial reference to the grinding of the inner diameter of flexible articles such as springs.

In the process of grinding the inner diameter of a spring or other tubular member upon an automatic machine such as the Heald centerless grinder, it is customary to place the article within a tubular pocket or cylinder, this being especially necessar when grinding a spring or similar flexible article. The pocket or cylinder containing the Spring is then fed automatically to the supporting structure of the machine while the grinding wheel is guided into position to grind its inner bore or surface. It has been the practice to employ a solid-walled metal tubular pocket for this purpose, the outer diameter of the pocket being ground to exact dimension with which the bore to be ground will have an exact relation. In manufacturing springs for some uses, as for use in spring clutches, it is necessary that the inner diameter be exactly symmetrical with the outer diameter and that the thickness or crosssectional area of the wire of which the spring is formed be of prescribed dimension, within very close tolerances. In some cases the outer surface of the spring is ground previous to grinding of the inner bore, which makes it possible to more easily control the grinding of the inner bore. However, slots or other irregularities in the outer surface would affect the grinding operation, except for the use of grinding cylinders.

In using the rigid, solid walled cylinders heretofore known, the machine operator experienced considerable difliculty in fitting the spring or other article into the cylinder or pocket, since the bore of the pocket and the outer diameter of the article were necessarily of practically the same dimension, in order to grind to the required mall tolerances. The same difiiculty was encountered in removing the article after the grinding operation. Pliers or other gripping tools were used, requiring an expenditure of a great deal of the operators time and considerably afi'ecting the production rate. In addition, the tools used sometimes damaged the ground surfaces, increasing wastage.

An object of the present invention is to provide an improvement in grinding processes and apparatus involving the use of a grinding cylinder or pocket into which a spring or other article to be ground may be quickly and easily inserted by hand by the operator without the use of special tools, and from which the article may be removed with equal facility, thus increasing the production rate and decreasing costs of manufacture.

It is a further object to provide, as a part of an apparatus for internal cylindrical grinding or finishing, an expansible pocket or cylinder which may be simply and inexpensively fabricated yet which will provide a sufliciently rigid close tolerance support for the work piece during the grinding operation.

In the drawing, Fig. 1 is an isometric perspective view of an improved grinding cylinder according to my invention; Fig. 2 illustrates the method of inserting or removing an article into and from the improved grinding cylinder; Fig. 3 is a diagrammatic view illustrating the relation of the cylinder to the principal operating parts of an internal centerless grinder.

The improved grinding cylinder or pocket illustrated in Fig. 1 comprises a tubular body I formed of a high grade steel, having both its inner and outer surfaces ground to specified dimensions with very close tolerances. The wall of the cylinder is split longitudinally for its entire length, the slot 2 being cut angularly from each end of the cylinder to form a substantially V-shaped cut. Two partial slots 3 are cut angularly with relation to the vertical planes of the ends of the cylinder, one from either end and extending approximately half the length of the cylinder. Through provision of these slots 2 and 3, the walls of the cylinder may be expanded for receiving an article, and by reason of the inherent elasticity of the metal employed, it will contract into tight engagement with the circumferential surface of the article inserted. In the same way, after the grinding operation, the cylinder may be expanded to allow removal of the article.

Cylinders of this type are particularly important for center grinding a tubular or circular member having an irregular outer surface, or a flexible article such as a spring. Such articles may be ground on an automatic centerless grinding machine without the use of a grinding cylinder or pocket but only when allowable tolerances are large. To grind such an article to close tolerances the support provided by the cylinder is necessary. Since the cylinder or pocket has been made with exact dimensions, the inner surface of the spring or other article inserted therein may be fabricated with equally close tolerances with respect to its outer diameter.

To illustrate the relation of the pocket or cylinder to the grinding operation, in Fig. 3 is shown diagrammatically the essential operating parts of an automatic machine in connection with which my invention is adapted to be used or practiced. The machine embodies a large regulating cylinder 6, a, supporting cylinder 5 and a pressure roll or cylinder 1, the latter being movable to allow work to be inserted into and removed from grinding position. The article to be ground is inserted into the grinding cylinder or pocket I, which is then fed into :the position shown, between the three cylinders, the pressure cylinder holding it tightly against the other two cylinders. The regulating cylinder revolves to cause rotation of the grinding cylinder or pocket. The rotating grinding wheel 8 is then moved axially with relation to the pocket 1, Within the bore of the article to be ground, its periphery being held in exact relation to the periphery of the regulating cylinder and consequently of the grinding pocket held thereagainst. Thus the inner diameter of the article Within the pocket is ground to exact dimensions with respect to the -outer diameter of the article.

Since close tolerances are essential, the article to be ground necessarily must fit very tightly within the pocket, yet must be easily inserted and removed to allow speed of operation. Insertion and removal of an article into and from the pocket-or-cylinder 'I may be easily and quickly done without the use of hand "tools or other equipment, as illustrated in Fig. 2. By gripping the cylinder and the article to be inserted, such as a spring A, one in each hand, and twisting the two members oppositely, the spring may he slid into the pocket, since the walls of the latter will expand sufficiently to decrease the frictional resistance between the mating surfaces. The spring may be removed from the pocket with equal facility after the grinding operation by the insertion of a finger into the bore of the spring to grip its inner wall, gripping the cylinder with the other hand, and exerting a twisting and axially diverse pressure on the two members. Both the insertion and removal may be done quickly and with relatively little effort, expediting the operation and increasing the production rate of the machine and operator.

By cutting the slots in the pocket on an angle with respect 'to the axis 'of the cylinder, the possibility of irregularity of the surface at any point on its periphery such as might cause an equivalent irregularity in the surface ground is eliminated, the pocket thus presenting in operative effect a continuous bearing surface against the surface of the regulating roll.

I claim:

1. In or for a combination comprising: (a) three spaced apart elements which in working position are arranged to make firm supporting and axis-locating contact with (b) a hollow work-holding cylinder of predetermined outer diameter and (c) a rotary metal-finishing tool located within and spaced from the cylinder eccentrically of its axis; the improvement consisting of forming the cylinder"b as a single piece of elastic material having a narrow slot extending obliquely for its full length and additional oblique slots each intersecting one end only of the cylinder, whereby a tubular work piece of approximately the same external diameter as the interior of the cylinder can be easily but firmly mounted in the cylinder and accurately finished internally by the finishing tool concentrically of the external surface of the work piece and then easily .removed from the cylinder.

2. In the process of internally grinding a generally cylindrical helical spring, the procedure comprising yieldably supporting the spring on its'ex'ternal peripheral surface and substantially throughout its length and circumference and then substantially non-yieldingly supporting the external peripheral surface of the yieldable support for the major part of its length during the grinding operation and at three circumferentially spaced regions of the support so located in reference to each other, as to maintain the spring on a fixed center.

3. In the process of grinding one peripheral surface of a cylindrical helical spring, the steps comprising forcing the other peripheral surface of the spring into telescoping snug contacting relationship to a radially expansible wholly elastic sleeve, mounting the sleeve on a series of supporting members spaced to make contact with the sleeve at three regions so as to hold the sleeve and spring telescoped thereby on a definite Working axis, rotating the sleeve and meanwhile applying a rotating grinding wheel to said one peripheral surface.

ROBERT L. YOUNG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 926,996 Shirley July 6, 1909 1,190,965 Sparr July 11, 1916 1,528,993 Samuel Mar. 10, 1925 2,280,620 Binns et al Apr. 21, 1942 2,283,424 Colwell et a1. May 19, 1942 2,382,311 Heald 'Aug. 14, 1945 FOREIGN PATENTS Number Country Date 673,419 Germany Mar. 22, 1939 

